The average person has 46 chromosomes, 23 from mom and 23 from dad. Babies born with Down syndrome, however, have 47 chromosomes. Lisa Shaffer learned this from a high-school biology textbook while growing up in the Tri-Cities. She read it. She saw a picture of a Down syndrome baby. More chromosomes should be good, she thought. Why isn’t it? The question fascinated her.

“I decided then that I was going to be a geneticist,” says Shaffer, now 46 years old. “My friends laugh. They claim I was the only one who knew what she wanted to be.”

While Shaffer knew what she wanted to be, she didn’t know what she would become: a successful businesswoman. Shaffer is the president and CEO of Signature Genomic Laboratories LLC, a quickly growing cytogenetic-testing company that has developed proprietary systems for diagnosing chromosomal abnormalities.

The 5-year-old company is on pace to test about 14,000 genetic samples this year, up from 10,300 tests in 2007 and an exponential increase from the 780 samples it tested in 2004, its first full calendar year in business. The company now employs 80 people, and its revenues are expected to hit $18 million this year, up from $13.5 million last year.

Inc. magazine recently ranked Signature Genomic 114th on its list of the 5,000 fastest-growing private U.S. companies. The magazine also ranked Shaffer eighth on its list of top female CEOs of the fastest-growing companies.

The daughter of a nuclear physicist and a schoolteacher, Shaffer was born in California, and her family moved to the Tri-Cities when she was 3 years old. When she graduated from high school in 1980, she says, schools didn’t offer bachelor’s degrees in microbiology or genetics, so she attended Washington State University and earned a degree in biology with an emphasis in genetics. Upon graduation, she entered the genetics doctoral program at the Medical College of Virginia, one of three schools in the U.S. at the time that offered such a degree, Shaffer says.

Upon receiving her doctorate in genetics, Shaffer accepted a position at Baylor College of Medicine, in Houston, and became clinical director of its cytogenetics laboratory.

She was in that position when Dr. Bassem Bejjani, who co-founded Signature Genomic with her, came to Baylor.

At that time, he says, “I was surprised that she was so young because she had been published so many times.”